There has been an increased demand for lightweight miniature tools with simplified internal working parts. Tools such as draftsmen's erasers that have a rotating head attached to a hand-held handle have been used for several years. Unfortunately, these hand-held tools were encumbered by an electrical line which had to be plugged into an AC outlet.
A need arose for a hand-held tool that could use standard direct current battery cells for powering the motor. To meet this demand, manufacturers assembled miniature hand-held tools that served the immediate purpose. However, they require electrical connection or wiring within the tool that complicated assembly and created electrical losses. The electrical losses caused increased demand on the battery cells, and accordingly, resulted in a shortened life for the battery cells in these applications.
A need has therefore risen for an improved hand-held battery-powered tool which does not have the unwanted internal wiring complications as do other battery-powered hand-held tools.
One aspect of the present invention comprises a battery-powered hand-held motor tool for rotating a bit and which generally comprises a substantially cylindrical-shaped housing having a direct-current motor mounted therein. As with most conventional motors, the motor has a shaft at one end and first and second terminals at its other end. The first and second terminals correspond to the positive and negative poles of the motor. Connected to the shaft is a substantially cylindrical-shaped collet for selective engagement with a bit. The bit may be one of a number of items, such as a drill or a sander.
To power the motor, a battery assembly having a plurality of battery cells contained therein is slidably engaged into the housing and clipped to the housing of the tool. The battery cells are conveniently recharged by a battery charger which has an AC wall plug integrally connected thereto for engaging into a standard AC outlet.
A substantially disc-shaped actuator is rotatably held in the housing. The actuator is coaxially aligned with the motor and battery assembly. In operation, the actuator is positioned between the motor and the battery assembly. The motor is electrically attached to the actuator at one end. The actuator has a first set of arms, a second set of arms and a third set of arms extending therefrom for selective electrical engagement with the battery assembly contacts. Specifically, the first, second and third sets of arms are selectively connected to the battery assembly contacts by rotation of the actuator to a first position in order to couple the batteries in series and cause the motor to rotate the bit at high speed. Additionally, the first and second sets of arms are selectively connected to battery contacts by rotating the actuator to a second position to contact the battery assembly such that the batteries are coupled in a parallel condition with the motor to rotate the bit at a low speed.
The present invention presents several technical advantages over the convention battery-powered hand-held motor tools.
Since the battery assembly is one piece, it can be easily removed from the housing and the battery cells can be recharged with the battery charger. In addition, because of the orientation of the battery cells within the battery assembly and the ability to have the actuator rotate to selectively contact the battery assembly, internal wiring can be greatly reduced, and accordingly, the load on battery cells can be reduced.